Disc mill



Feb 7, F. R. FEDER AL DISC MILL Filed Feb. 18, 1964 5 Sheets-$heet lINVENTORS FRIEDHELM R. FEDER JOHN R. THOMAS w. E. WILLOUGHBY BY %W//M ATTORN Y.

Feb. 7, 1967 DISC MILL Filed Feb. 18, 1964 F. R. FEDER ETAL 3Sheets-Sheet 2 V ATTOR Y.

DISC MILL Filed Feb. 18, 1964 3 Sheets-Sheet 5 F160 5.. 9 FIG 6. FIG. Z

CONTROLLER TIMER -70 n INVENTORS FRIEDHELM R. FEDER 5 .r- JOHN R. THOMASBY 68 7 W. E. WILLOUGH ATTO NEY.

United States Patent 3,302,893 DISC MILL Friedhelm R. Feder, Westfield,N.J., John R. Thomas,

Elmhurst, Pa., and William E. Willoughby, Bernardsville, N.J., assignorsto Wedco, Iuc., Garwood, N.J., a corporation of New Jersey Filed Feb.18, 1964, Ser. No. 345,740 13 Claims. (Cl. 241-37) This inventionrelates to disc mills and more particularly to disc mills suitable forthe working of plastics.

Disc mills for the size reduction and working of pulp and meal are veryold. In recent years these mills have been used for size reduction ofplastics. For example, plastics are readily available for primaryreducers in a so-called pellet form, i.e. particle about minus flp-minus inch, and for some uses of the plastic it is desired that it beprovided in much finer form, e.g. powder form.

It has been observed that the known disc mills have disadvantages whenutilized for working plastics. Thus, the plastics which are commonlytreated are thermoplastic materials and a problem arises with respect toheat generation in that in the working of the material, the temperatureis frequently raised to such a point that the material becomes plasticand the particles coalesce. This occurrence of course amounts to a grossinterference with the processing and requires interruption of theoperation of the mill for cleaning to free the working surfaces of themill of adhering plastic material and to remove from the mill theglomerates of plastic which are formed upon the coalescence. In order toavoid the overheating of the plastics, it is common, when utilizingmills of known construction, to operate the mill at a throughput ratevery substantially below what can be denominated the full capacity ofthe mill.

Accordingly, a principal object of the instant invention is to provide adisc mill construction particularly adapted to the processing of plasticmaterials, and which construction permits operation at near capacity ofthe machine. A further principal object of the invention is to provide adisc mill construction characterized in that upon overheating of theplastic material being worked, so that agglomeration of the materialoccurs, necessitating a shutdown and clean-up of the equipment, thiswork can be performed readily without the necessity of laying theequipment olf for a prolonged period.

The manner in which these and other objects are attained, will beapparent from the following description taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a side elevation, partially in section, showing an embodimentof apparatus according to the invention;

FIG. 2 is a cross-section view taken along line 22 in FIG. 1;

FIG. 3 is a cross-section view taken along line 33 in FIG. 2;

FIG. 4 is a cross-section view taken along line 4-4 in FIG. 1;

FIG. 5 is a front elevation view of one of the discs of a disc mill andis shown in FIG. 1;

FIG. 6 is an enlarged view of a portion of the apparatus shown in FIG.1, more particularly, of the working faces of the discs shown in FIG. 1;

FIG. 7 is an enlarged view of a portion of a working face of a disc asis utilized in apparatus according to the invention;

FIG. 8 is a cross-section view taken along line 8-8 in FIG. 7; and

FIG. 9 is a schematic view of a control arrangement for the apparatusshown in FIG. 1.

In the drawings, like reference characters refer to corresponding parts.

According to the invention a disc mill includes a first disc and asecond disc, and the discs are mounted in opposed relation, as isgenerally true for disc mills. A first shaft is provided and has thefirst disc mounted thereon, and this shaft extends axially outwardlyfrom the disc mounted thereon. A second shaft is provided for the seconddisc, and the second shaft extends axially outwardly from its disc. Thetwo shafts extend axially outwardly of the opposed discs in oppositedirections. One of the disc-shaft pairs is mounted on a support andmeans are provided for moving this support relative to the other disc sothat the supported disc can be moved toward and away from the other discalong a defined path. Fluid pressure means are provided for urging themovably supported disc toward the second disc, and spacer means areprovided for limiting travel of the movable disc toward the stationarydisc in response to urging of fluid pressure means, and, thereby, asuitable spacing of the discs for milling is obtained. Load sensingmeans are provided for sensing overload of the mill, and, further,overload relief means are provided. The overload relief means areconnected to the load sensing means for response to the load sensingmeans, and are effective in response to control the fluid pressure meansupon occurrence of overload to move the discs apart for relief of theoverload and to then move the discs together to the milling spacing.

Referring to the drawings, the device there shown includes a disc millassembly 11 wherein the first disc 15 and the second disc 16 arecontained in a casing 13 having a closure 14. The first disc 15 isfixedly mounted on shaft 17 for rotation therewith, and the second disc16 is fixedly mounted on shaft 18 for rotation therewith. The shafts 17and 18 extend axially outwardly in opposite directions from the opposeddiscs 15 and 16. The first disc 15 is made up of the support ring 19,disc spokes 20, and the disc working face 21 which is bolted to thesupport ring 19. The second ring 16 is made up of the support 22 and theworking element 23, which is bolted to the support 22. A feed baffle 24is secured to the closure 14 and terminates in the peripheral portion 25which extends into the spokes 20. The feed baflle 24 serves to directfeed to the mill to between the discs, and this feed baflle constructionis known in the art. A feed pipe 27 passes through the closure 14 andthe baffle 24 and serves to direct feed to within the baffle, and thebaffle, in turn, serves to direct the feed toward the discs. The feedflows from the space enclosed by the baflle 24 to between the spokes 20and on to between the discs and is then exposed to the working action ofthe mill.

The shaft 18 on which the second disc 16 is mounted, is journaled in thejournal blocks 28 and 2-9 and this shaft is provided with a drive wheel30 which is connected to a motor 31 by belt 32. The motor 31 can be avariable speed motor. The journal blocks 28 and 29 are mounted on theframe 12, respectively, by supports 33 and 34, and the motor 31 is alsosecured to the frame 12 by the support 35. The shaft 18 is provided witha bore 36 which extends axially therethrough and communicates at theouter end with fluid conduit 37, and at the inner end with the annularslot 38. Radially outwardly extending tubes 39 communicate with the slot38 at one end thereof, and, at the other end thereof, communicate withthe outlets 40 which are disposed at spaced intervals about the workingface 23 of the second disc 16. 'Fluid, gas or liquid, for cooling can beintroduced into the bore 36 from the fluid conduit 37, and can pass fromthe bore 36 via the passageways 39 to the outlets 40, so that such fluidis introduced into the vicinity of the working of the material andcooling can thus be eflected by the fluid.

The shaft 17 on which the first disc is mounted extends through journalblock 41 and journal block 42. A drive wheel 43 is mounted on the shaftand this drive wheel is connected with the motor 44 by drive belt 45.The motor 44 can be a variable speed motor. The journal block 41 issecured by bolting 46 to the disc assembly closure 14, and this journalblock, as well as journal block 42 is mounted on the car 48 which, as ismore fully described hereinafter, serves for carrying the parts mountedthereon. The motor 44 rests on bed plate 49, and this bed plate issupported by the uprights 50. The car 48 includes runner 51 which isslidably mounted on the track 53. Thus, by movement of the car over thetrack 53, the motor 44 and the shaft 17 together with the partsassociated therewith including the first disc 15 and the closure 14 canbe moved relative to the second disc 16 and the casing 13, and the partsassociated with the second disc 16, including the shaft 13.

The means provided for moving the car can be best seen in FIG. 2, FIG.3, and FIG. 4. Thus, mounted on the frame 12 is the track 53 having sideextensions 54 which are bolted to the frame 12. The car includes runners55 which are formed so as to be received in complementary manner by thetrack 53, and the runners 55 are slidably movable over the track 53. Theframe 12, the track 53, and the runners 55 are provided, respectively,with cross-pieces 12a, 53a, and 55a. Mounted on the track cross members53a is the cylinder piston assembly 56, by bolting 57, and this assemblyincludes the piston rod 58 which has mounted on the end thereof theflange 59. The flange 59 is secured to the cross member 55a of the car.The car can be moved over the track by operation of the piston-cylinderassembly.

In the embodiments shown, the piston-cylinder assembly 56 is a hydraulicarrangement, and this assembly includes as well as the piston rod 58,the piston 60. Hydraulic fluid is maintained on each side of the piston60 and is supplied to one side thereof by hydraulic fluid supply lines61, while it is supplied at the other side thereof by hydraulic fluidsupply line 62.

Referring to FIG. 1, by suitable operation of the piston-cylinderarrangement 56 shown in FIG. 2-FIG. 4, the car can be moved back andforth on the track 53 and thus the first disc 15 can be moved toward andaway from the second disc .16, since the disc 15 is mounted on the car.An adjustable stop means 63 is secured to the track 53 and serves tolimit the extent to which the car can travel to the right, as is shownin FIG. 1. Thus, the extent to which the first disc can be moved towardthe second disc can be controlled by the stop means 63. This stop meansis adjustable so that the spacing between the discs 15 and 16 can becontrolled by manipulation of this stop means. A micrometer-typeadjusting means can be provided so that the spacing of the disc platescan be selected in units of 0.001 inch. Outfitted with a stop means,such as stop 63, the device can be operated in the manner that thepiston-cylinder arrangement normally urges the first disc 15 toward thesecond disc 16 and so that the runner 5.1 of the car is normally inabutting relation with the stop means 63. Further, means can be providedso that in the event of an overload on the machine as may occur when thefeed rate becomes excessive, the piston-cylinder arrangement can beactuated so that the car moves to the left (as shown in FIG. 1),whereupon the first disc 15 moves away from the second disc 16 so as torelieve the overload. Upon relief of the overload, the piston-cylinderarrangement can be actuated to return the car to its normal positionwith the runner 51 abutting with the stop means 63. Desirably, the meansfor occasioning the movement of the first disc 15 away from the seconddisc 16 upon the occurrence of overload, is provided so that upon suchoperation the device goes through a cycle wherein the first disc movesaway from the second disc 16 and then returns to its normal workposition, all automatically.

A further feature of the disc mill according to the invention, is thatthe mill can be conveniently opened up to provide access to the insidethereof. Thus, the device can be constructed so that when it is desiredto open the mill to expose the working surfaces of the disc, the usualoverload control means can be disconnected, and the piston-cylinderarrangement 56 can then be actuated to move the discs apart a distancesuch that they are exposed for working. Thus, to service the discs, thecar on the track 53 can be moved to the extent that the closure 14 ofthe disc mill assembly is removed from the casing 13 and the first disc15 is moved to without the casing 13.

In the normal running operation wherein provision is made for relievingoverload, the closure 14 does not move to the extent that the disc millassembly is opened. An overlap is provided so that the closure .14 maymove an amount appropriate to relieve the overload while at the sametime the casing is not opened. Thus, the casing 13 is provided with theangle iron seat 64 and the closure 14 is provided with the extension 65,and the extension 65 is slidable in the seat 64 and is closefittingtherein, so that as the closure 14 moves back and forth in the relief ofoverload, the extension 65 slides back and forth in the seat 64, but isalways in engagement therewith.

A control arrangement suitable for facilitating operation of the mill asis described above is set forth schematically in FIG. 9. Each side ofthe piston 60 of the piston-cylinder arrangement 56 is filled withhydraulic fluid, and the corresponding fluid bodies are maintained undersuitable pressure by auxiliary cylinders 75 and 76 which communicate,respectively, with the two sides of the piston 60, via lines 77 and 78.The auxiliary cylinders, in turn, are maintained under pressure by theair cylinders 73 and 74 which are communicated with the air accumulator67 and the air compressor 66 by, respectively, air lines 69 and 70, andthe manifold line 68. A pressure differential across the piston 60 ismaintained so that in normal operation the first disc member 15 is urgedtoward engagement with the second disc member 16 and so that the runner51 of the car is urged into abutting relation with the stop means 63. Toprovide the desired cyclic operation for relief of overload, means areprovided for sensing the overload, and in the embodiment illustrated,this detection is provided by ammeter 87, in the lines 89, to the motor44. Upon the occurrence of overload, current will increase. The ammeterwill sense the increase in current, and is connected by line 91 to thecontroller 93 so that upon the occurrence of an overload, the ammeterwill actuate the controller. The controller can include a sensitivitymeans, for example a time delay, so that operation thereof is dependenton the overload existing for more than say about to 15 seconds, commonlyabout 3 seconds. Power is introduced into the controller via line 99 andthe controller is connected to solenoid valves 71 and 72 in,respectively, lines 69 and 70 by, respectively, power lines 97 and 96.Further, operation of the controller 93 in response to overloadoccasions activation of the timer 95 which serves to provide the desiredtiming for the cycle. Thus, each of the valves 71 and 72 is a two-way,three-position valve. In one position, each of these valves communicatesthe inlet and outlet side of the air line with which it is connected,and in its other position it communicates the low pressure side of itsair line with the atmosphere to release air from the low pressure side(the piston-cylinder arrangement 56 side). As illustrated in thedrawing, upon occurrence of overload, the piston rod 58 initially movesto the left to occasion separation of the discs, and following suchmovement, the piston rod moves to the right to bring the discs back tothe working position. Upon the occurrence of overload, excessive currentis taken by both of the motors 44 and 31 and this is sensed by theammeter 87 in the power line of the motor 44. Thereupon the controller93 is actuated so that the valve 72 is moved to communicate the highpressure side of line 70 with the low pressure side thereof, i.e. tocommunicate the compressor 66 with the air cylinder 74. Air pressurethen effects an increase of hydraulic pressure in the system made up ofthe line 78 and the hydraulic fluid on the right hand side of piston 60,as shown in FIG. 9. At the same time, the controller 93 effects theoperation of the valve 71 so that the low pressure side of line 69 iscommunicated with the atmosphere. Under such conditions, the piston 60is moved to the left occasioning the separation of the discs. Duringthis operation, the timer 95 is itself in operation and automaticallyoccasions reversal of the operation of the valves 71 and 72, so thatafter a short time interval, the positions of these valves are reversedso that the piston 60 is moved towards the right (as shown in FIG. 9)whereupon the car on the track 53 is moved to the right (as is shown inFIGURE 1) to bring the discs back to their working position. At thispoint in the cycle, the runner 51 of the car is in abutting relationwith the stop means 63 and the desired spacing is provided. The timercan be set so that the discs are separated about 7 at maximum opening.Purging results and thus overload is relieved.

The invention further provides for the separating of the discs to theextent that the internals of the disc assembly are exposed forservicing. This separating of the discs can be accomplished by operationof the pistoncylinder arrangement 56. Thus, the power line 91interconnecting the controller 93 with the ammeter 87, is provided witha switch 92, and the line interconnecting the controller 93 with thetimer 95 is provided with a switch 94. These switches are normallyclosed, but can be opened to permit separating of the discs forfacilitating servicing of the device. Upon opening of the switches, theswitch 99 which interconnects the controller 93 with the manualoperating panel 101 can be closed. The manual operating panel 101 canthen be used as a control center for manually selecting the positioningof the valve 71 and 72 to manipulate these valves so as to providesuitable pressure to the piston-cylinder arrangement 56, whereby thedesired actuation of the piston 60 can be made so as to effect theseparation and subsequent bringing together of the discs.

The control arrangement further provides for the maintaining of selectedpressures on each side of the piston 60. Thus, the pressure sensinginstruments 81 and 82, powered respectively by lines 03and 84, areconnected to the respective sides of the piston 60. Power lines 85 and86 connect the pressure sensing instruments 81 and 82, respectively,with the power lines 96 and 97 of the solenoid valves 72 and 71. Thepressure instruments 81 and 82 are each operative over a selected narrowpressure range to occasion prcssurizing of the cylinder as is desired tomaintain the selected pressure on each side of the piston 60. The powerlines 85 and 86 which interconnect the pressure instruments 81 and 82with the appropriate valves pass through the switch 100. Switch 100 isactuated by the flanges 59 on the piston rod 58 so that the circuitthrough lines 85 and 86 is closed when the car is in the normal workingposition on the tracks 53, but is open when the car is moved to the left(FIG. 1). Thus, when the piston-cylinder arrangement is in operation torelieve an overload, the switch 100 will be opened and the controls forthe overload will be effective to control operation and the pressureinstruments 81 and 82 will be ineffective to control operation.

The valves 71 and 72 are biased to the position wherein the pressuresupply system made up of the compressor 66 and the accumulator 67 isisolated from the air cylinders 73 and 74 so that when the variouscontrol devices are not operating, the piston-cylinder arrangement isisolated from the air supply system.

A further feature of the mill of the invention is the manner in whichthe discs are constructed. Thus, the discs each have a toothed areadisposed in an annulus adjacent the outer periphery thereof, and thetoothed portions of the two discs are opposed to each other for workingof the material to be milled. The space between the discs inwardly ofthe toothed areas is open and free for movement of material introducedbetween the discs to the toothed areas. That is, radially extendingpaddles or the like, as are commonly used in disc mills to move materialto the periphery of the discs and to themselves effect a size reduction,are not utilized and the space between the discs is left free for travelof the material to the working surface by gravity, air currents, andcentrifugal force. Further, the toothed areas are inclined toward eachother and the toothed area of one of the discs terminates radiallyinwardly of the toothed area of the other of the discs.

As can be seen in FIG. 1, the second disc 16 is made up of a supportingmember 22 which can be a solid casting, and the ring member 21 whichbears the working surface of the disc, this working surface being likethe corresponding part of the other disc, shortly to be described.

The disc 15 is made up of a supporting member 19 and the spokes 20, andthe working ring 21. See FIG. 5. Further, a hub 103 is provided. Thespokes 20 provide the intermediate spaces 104 which permit passage ofmaterial through the disc 15 to between the two discs. The workingsurface 21 is made up of a toothed area disposed in an annulus adjacentthe outer periphery of the disc, and, as can be best seen in FIG. 6, theannular toothed area of one of the discs terminates radially inwardly ofthe toothed area of the other of the discs. Such construction obviatesthe necessity for maintaining close tolerance insofar as the outer edgesof the working surfaces are concerned. The configuration of the workingteeth can be seen in FIG. 7 and FIG. 8. Thus, the working surface 21 ofthe disc 15 is made up of the radially extending teeth 105 as is shownin FIG. 8. The working surface of the other disc is of likeconfiguration.

Example and differing in diameter by about /2. Two 50 horse-- power 1750rpm. motors can be used. The motor can be connected so that peripheraldisc speeds of up to about 25,000 feet per minute (relative peripheralspeed, about 50,000 feet per minute) are obtained. In operation a vacuumcan be drawn on the equipment to facilitate'removal of the milledmaterial. A vacuum reducing the pressure on the downstream side of thediscs by 20 inches of water can be used. This can be provided byapplying suction to the discharge line 10 (FIG. 1) for the milledmaterial.

A bore 9 can be provided in the closure 14 to provide air for sweepingthe material from the mill and of course some air is drawn through themill with the feed. A vibrating feeder (not shown) can be used to feedthe material to be milled through feed line 22. The motors arepreferably variable speed motors and throughput can be as follows. Formilling low or medium density polyethylene to reduce pellets of size Mato A" to about 20 to 200 mesh, at a disc r.p.m. of 2200-3000 thethroughput can be about 1500 to 250 pounds per hour. The throughput atthe r.p.m. employed can be very close, say to within a fraction of apercent, preferably less than about 0.1% of overload throughput, sincethe machine automatically relieves overload without substantialinterference with operation. The normal spacing of the discs (spacingduring normal running condition) can be about .001-.090". Operationdescribed here is without use of coolant as can be introduced throughshaft 18. Conventional recycle procedures can be used to return oversizematerial to the mill. Thermoplastics other than polyethylene can beworked and non-thermoplastics can also be worked.

While the invention has been described in reference to particularembodiments thereof, these embodiments are merely representative, and donot define the limits of the invention.

What is claimed is:

1. A disc mill comprising:

(a) a first disc and a second disc, said discs being mounted in opposedrelation, a first shaft having said first disc mounted thereon andextending axially outwardly from the opposed discs, a second shafthaving said second disc mounted thereon and extending axially outwardlyof the opposed discs in a direction opposite to the direction in whichthe first shaft extends,

(b) means for driving each of said shafts to rotate the discs inopposite directions,

(c) a support for said first shaft and its disc and means for movingsaid support relative to the second disc for axially directed movementof the first shaft and its disc away and toward the second disc along adefined path,

(d) fluid pressure means for urging the movably supported disc towardthe second disc,

(e) spacer means for limiting travel of the first disc toward the seconddisc in response to said urging of the fluid pressure means and toprovide the discs spaced for milling,

(f) load sensing means for sensing overload of the mill, and overloadrelief means connected to the load sensing means for response to theload sensing means and effective in response to control said fluidpressure means upon occurrence of overload to move the discs apart forrelief of the overload and then move the discs together to the millingspacing.

2. Disc mill according to claim 1, said fluid pressure means consistingessentially of a hydraulic piston-cylinder assembly, means for applyinghydraulic pressure to each side of the piston, said overload reliefmeans in control of the fluid pressure means, varying the pressure oneach side of the piston to provide said movement for relief of overloadand return to milling spacing.

3. Disc mill according to claim 1, said means for driving the first disccomprising a motor, said motor being mounted on said support formovement therewith.

4. Disc mill according to claim ll, said means for driving the shaftsincluding at least one motor.

5. Disc mill according to claim 4, said load sensing means consistingessentially of an ammeter for sensing current to said motor.

6. Disc mill according to claim 1, said support being movable along saiddefined path a distance effective to separate the discs to expose themfor servicing.

7. Disc mill according to claim 1, a casing for the discs and a closurefor said casing, one of the closure and casing being mounted formovement with said first disc, the

other of the closure and casing being mounted in an axially fixedposition, an overlap fit between the closure and casing sufficient toprevent opening of the casing upon movement as aforesaid for relief ofoverload, said support being movable along said defined path to removesaid closure, opening said casing and moving said first disc to withoutthe casing to open the casing and separate the discs to expose them forservicing.

8. Disc mill according to claim 7, said fluid pressure means consistingessentially of a piston-cylinder assembly, means for applying fluidpressure to each side of the piston, said overload relief means incontrol of the fluid pressure means varying the pressure on each side ofthe piston to provide said movement for relief of overload and return tomilling spacing, means for disconnecting the load sensing means and thefluid pressure means, and means for actuating the fluid pressure meanswhen disconnected from the load sensing means to separate said discs toexpose them for servicing as aforesaid.

9. Disc mill according to claim 8, said fluid pressure means being ahydraulic fluid pressure means.

10. Disc mill according to claim 1, the spacer means being adjustable topermit selection of milling spacing.

11. Disc mill according to claim 3, said means for driving said seconddisc comprising a motor fixedly mounted with respect to the second disc.

12. Disc mill according to claim 1, the discs each having a toothed areadisposed in an annulus adjacent the outer periphery thereof, the toothedportion of the two discs being opposed to each other for working of thematerial to be milled, the space between the discs inwardly of thetoothed areas being open for free movement of material introducedbetween the discs to the toothed areas.

13. Disc mill according to claim 12, the toothed areas being inclinedtoward each other, the toothed area of one of the discs terminatingradially inwardly of the toothed area of the other of the discs.

References Cited by the Examiner UNITED STATES PATENTS 2,216,611 10/1940Dimm 241-256 X 2,887,277 5/1959 Sakata 241-37 2,971,704 2/1961 Johansson241-37 3,040,996 6/ 1962 Ginaven 241-251 3,129,898 4/1964 Michel 241-2563,207,450 9/1965 Horstman 241-251 3,212,721 10/1965 Asplund 241-37FOREIGN PATENTS 946,390 1/1964 Sprout.

ROBERT C. RIORDON, Primary Examiner.

D. KELLY, Assistant Examiner.

1. A DISC MILL COMPRISING: (A) A FIRST DISC AND A SECOND DISC, SAIDDISCS BEING MOUNTED IN OPPOSED RELATION, A FIRST SHAFT HAVING SAID FIRSTDISC MOUNTED THEREON AND EXTENDING AXIALLY OUTWARDLY FROM THE OPPOSEDDISCS, A SECOND SHAFT HAVING SAID SECOND DISC MOUNTED THEREON ANDEXTENDING AXIALLY OUTWARDLY OF THE OPPOSED DISCS IN A DIRECTION OPPOSITETO THE DIRECTION IN WHICH THE FIRST SHAFT EXTENDS, (B) MEANS FOR DRIVINGEACH OF SAID SHAFTS TO ROTATE THE DISCS IN OPPOSITE DIRECTIONS, (C) ASUPPORT FOR SAID FIRST SHAFT AND ITS DISC AND MEANS FOR MOVING SAIDSUPPORT RELATIVE TO THE SECOND DISC FOR AXIALLY DIRECTED MOVEMENT OF THEFIRST SHAFT AND ITS DISC AWAY AND TOWARD THE SECOND DISC ALONG A DEFINEDPATH, (D) FLUID PRESSURE MEANS FOR URGING THE MOVABLY SUPPORTED DISCTOWARD THE SECOND DISC,